The present invention relates to a vehicle operation assist control system, and in particular to a vehicle operation assist control system that detects an obstacle ahead and helps the vehicle operator take a corresponding evasive action.
Various proposals have been made in connection with the systems known as ITS which are highly effective in preventing traffic accidents. For instance, copending U.S. patent application Ser. No. 09/985,635 filed Dec. 5, 2001 discloses a vehicle operation assist control system which detects an obstacle ahead and helps the vehicle operator take an evasive action. According to this prior proposal, when an obstacle is detected ahead, the steering angle is directly controlled and a corresponding yaw moment is applied to the vehicle or the steering assist force is controlled so as to cause the vehicle to take a path that evades the obstacle.
The evasive motion of the vehicle can be defined by the lateral motion or lateral acceleration of the vehicle. On the other hand, in assisting the vehicle operation, an evasive motion of the vehicle can be favorably accomplished by controlling the fore-and-aft forces of the tires. Based on such considerations, a vehicle operation assist control for evading an obstacle ahead can be favorably executed by converting the required lateral acceleration into a corresponding vehicle yaw rate, and applying a yaw moment to the vehicle so as to achieve such a yaw rate. However, in practice, due to the time delay in the control system, there is some difficulty in ensuring a required response speed for the evasive action. Depending on the particular condition, an evasive action may simply fail to be taken altogether, a discomfort may be caused to the vehicle operator, or the margin of the evasive action may be too small to be accepted.
In view of such problems of the prior art, a primary object of the present invention is to provide a vehicle operation assist control system which allows a highly responsive evasive action to be taken in evading an obstacle ahead.
A second object of the present invention is to provide a vehicle operation assist control system which can favorably utilize a right and left drive force splitting system or a right and left independent brake system.
A third object of the present invention is to provide a vehicle operation assist control system which is both economical and practical to implement.
According to the present invention, such objects can be accomplished by providing a vehicle operation assist control system for assisting the operation of a vehicle, comprising; vehicle operation assist control system for assisting the operation of a vehicle, comprising; means for acquiring information on an obstacle ahead, the information including a distance to the obstacle and a width thereof; means for determining an evasive path of the vehicle for avoiding the obstacle according to the distance to the obstacle and the width thereof; means for computing a lateral acceleration for enabling the vehicle to follow the evasive path; means for converting the lateral acceleration to a yaw rate under a static condition; means for adding a phase advance term to the yaw rate; means for computing a yaw moment for achieving the yaw rate having the phase advance term added thereto; and means for producing the computed yaw moment in the vehicle.
This provides a vehicle operation assist control system which allows an obstacle to be evaded in a highly responsive manner, and such a system can be implemented as a relatively simple control system. Computer simulations have demonstrated that such a favorable system response can be obtained in a highly stable manner. To minimize the amount of computation, the path of the evasive motion may be defined as a simple sinusoidal mathematical function.
The means for acquiring information on an obstacle ahead may consist of a radar using ultrasonic wave, electromagnetic radiation or laser radiation, or an imaging device. Other functional means of the system according to the present invention may be implemented with a computer operating under appropriate programs.
The means for producing the computed yaw moment in the vehicle may comprise a right and left traction splitting device and/or a brake system capable of controlling the right and left brake forces independently.